1. Field of the Invention
This invention relates to a watertight slide fastener for a wet suit, a waterproof bag or other articles needed to be watertight and airtight.
2. Description of the Related Art
This type of watertight slide fastener is currently known in which a U-shape top stop for receiving a slider body when the slide fastener is closed is mounted on a surface of a slide fastener chain (Japanese Patent Publication No. 22686/1970). Another watertight slide fastener of the described type is known in which a top stop is composed of an inner seal portion for being fitted in an opening between upper and lower wings of a slider body and an outer seal portion for tightly closing the opening, the outer seal portion having a pair of arcuate projections extending inwardly from opposite ends of the outer seal portion for contacting opposite side walls of guide flanges of the slider body (Japanese Utility Model Laid-Open Publication No. 103411/1988).
In the first-named prior watertight slide fastener, the slider itself has an ordinary shape rather than a unique shape, and the U-shape top stop for merely receiving the slider body is mounted on the top end of the slide fastener chain. Partly since the slider body is merely engageable with the top stop and partly since such engagement takes place only at the surface of the fastener chain, the slider body tends to be inclined or move when an external force is exerted on the surface of the slider body, so that the slide fastener cannot be closed with perfect watertightness.
Also in the second-named prior watertight slide fastener, in which the slider itself has a very ordinary type, partly since the guide flanges of the slider body are merely engageable with the arcuate projections of the opposite end of the outer seal portion and partly since there is no locking and retaining means between the slider body and the top stop, the slider tends to move so that the slide fastener cannot be closed with perfect watertightness. Additionally since only the opening between the upper and lower wings of the slider body is to be closed, only an inadequate degree of watertightness can be achieved.